[unreadable] There are over 2000 catheterization laboratories in the U.S. performing over 1 million coronary catheterizations and an equivalent number of non-coronary catheterization procedures per year. Science Research Laboratory (SRL) proposes to develop an improved digital imaging technique for visualizing contrast-filled structures that could be applied in all cases where contrast imaging is currently used with many advantages over current techniques. The technique, Dual-Energy Digital-Subtraction Angiography (DEDSA), uses a proprietary x-ray source that relies on novel anode coatings and x-ray filters to enhance the sensitivity to contrast agent while suppressing features due to tissue and bone. The source technology also can be applied to dual-energy contrast enhanced digital subtraction mammography (CEDSM), which has only recently been demonstrated. SRL has demonstrated DEDSA imaging of iodine contrast agent within calibrated anthropomorphic phantoms as well as within excised animal organs. In this program we will demonstrate the capability of using gadolinium contrast agents as well. Gadolinium compounds (such as Gd-DTPA) offer many advantages over iodine for DEDSA imaging, including improved tissue cancellation and lower patient dose, and are currently widely used as MRI contrast agents. The goal of this program is to develop and demonstrate a prototype DEDSA x-ray source capable of being used for real-time subtracted imaging. The source is based on electron bombardment of exotic anode materials, one of which was demonstrated at high power in Phase I, and the rest of which will be developed in Phase II. Once this source is developed it will be optimized and used to demonstrate and perfect DEDSA imaging using iodine and gadolinium contrast agents. [unreadable] [unreadable]